Raw materials, including iron ore, limestone, and coke are added to a blast furnace where they are heated. As the raw materials are heated, molten iron forms at the bottom of the blast furnace and a layer of slag forms on top of the molten iron. After a sufficient volume of molten iron builds up at the bottom of the blast furnace, the blast furnace is tapped to remove the molten iron. A tap drill is used to tap the blast furnace by drilling out the tap hole. As the tap drill is removed, molten iron flows through the tap hole into a trough where it is routed to a waiting rail car.
When all of the molten iron is drained out of the blast furnace, or after a desired amount of iron has been drained from the blast furnace, the tap hole is sealed. The tap hole is sealed with a mud gun. An anhydrous mixture, commonly referred to as “mud” or “clay” is loaded into the mud gun. The mud gun rotates from a non-operating or resting position to its operating position. In its operating position the mud gun is positioned so that the nozzle 110 (FIG. 1) of the mud gun (not shown) is aligned with the tap hole 130. Mud 170 is extruded through the nozzle 110 and forced into the tap hole 130. The mud 170 forces the residual molten iron 160 and slag 150 that is in the tap hole 130 back inside the furnace 140. Inevitably, however, not all of the iron 160 and slag 150 is pushed back into the furnace 140 i.e., some of the iron 160 or slag 150 remains in the tap hole 130 and mixes with the mud 170 forming a mud and ore residue 180. The mud gun nozzle 110 remains in place until the mud 170 dries or cures. After the mud 170 is cured, the mud gun is rotated back away from the blast furnace 140.
The mud and ore residue 180 in the tap hole 130 cause binding and wear on the tap drill (not shown) during the subsequent tapping of the blast furnace 140. In addition, the mud and ore residue 180 causes the drill to walk resulting in an irregular shaped, or oversized hole. This is undesirable because the size of the drilled hole controls the speed of the flow of molten iron 160 out of the blast furnace.
In addition, as the nozzle 110 nears the tap hole 130, the nozzle 110 comes into contact with the molten iron 130 and slag 150. Overtime, the tip of the nozzle 110 deteriorates and the mud gun nozzle 110 must be replaced. The deterioration is often referred to as rat toothing, because the lower portion of the nozzle tip which routinely comes into contact with the molten iron 160 is eroded faster than the upper potion of the nozzle tip which occasionally comes into contact with the molten iron. Replacement of the mud gun nozzle 110 is expensive and time consuming.
In operation, prior to rotating the mud gun into position to plug the tap hole 130, the operator ensures that the mud 170 is at the end of the nozzle 110. Mud 170 at the end of the nozzle 110 prevents molten iron 160 from entering and deteriorating the nozzle 110 when the mud gun is rotated into position. However, as the mud gun rotates into position, mud 170 occasionally falls out of the nozzle 110 and into the trough 120. The mud 170 contacts the molten iron 160 and slag 150 and creates black smoke. This smoke often results in the environmental protection agency (EPA) issuing a fine to the steel manufacturer.